Sealed condenser and shield for spark plugs



4, 1953 E. c. KIEKHAEFER 2,643,030

SEALED CONDENSER AND SHIELD FOR SPARK PLUGS Filed April 25, 1951 T Z I fINVENTOR.

I filt'orneys Patented Aug. 4, 1953 OFFICE SEALED CONDENSER AND SHIELDFOR SPARK PLUGS Elmer C. Kiekhaefer, Cedarburg, Wis.

Application April 23, 1951, Serial No. 222,446

3 Claims. 1

This invention relates to ignition systems and particularly to theprovision and placement of a small condenser in the ignition circuit ofthe spark plug of internal-combustion engines.

The invention provides a sealed, small capacitygap condenser immediateto the spark plug resiliently carried and supported by the spark plug ina rubber casing which serves as a water-tight covering for the sparkplug.

An object of the invention is to dispose the condenser in the electriccircuit as close to the spark plug as possible for optimum sparkdischarge and fuel ignition and at the same time to isolate thecondenser from the vibration and heat of the engine.

A further object is to protect the condenser against the vibration ofthe engine and against damage by rough handling or breakdown by thevibration of the engine.

A further object is to prevent the vibration of the engine fromultimately causing breakdown of the sealing means closing the condenserto the air. 1

Another object is to protect the condenser unit against fouling as bycorrosion of the metal parts or contamination of the ceramic parts ofthe condenser.

Another object is to assure the full electrical connection of thecondenser in the circuit with the spark plug and eliminate unnecessaryterminal fastenings.

These and other objects and advantages will be more fully set forth inthe following description of a preferred embodiment of the invention asillustrated in the accompanying drawing.

In the drawing:

Figure 1 is an elevational view of the engine spark plug and the sealedcondenser unit connected in series with the end of the lead wire andshowing the spark plug terminal connector and rubber casing in section;and

Fig. 2 is an enlarged view of the terminal connector and the condenserin transverse section to show the construction of the condenser.

The engine spark plug I, shown in the drawings, includes the metalhexagonal base 2 having a threaded lower end 3 for securing in the usualcylinder head or block of an engine, not shown.

The ceramic insulator 4 carried by base 2 extends a substantial heightfrom base 2 and en.- closes the electrical conductor rod 5. The upperterminal 6 of rod above insulator 4 and at the upper end of the sparkplug includes an annular groove 1 for receiving a detachable connectionto a sourc o g p n a current The lower end of rod 5 projects centrallyfrom the insulator in base 2 at the lower end of the spark plug. Theprojecting metal electrode 8 secured to base 2 extends to a pointbeneath or adjacent to the lower end of rod 5 and is accurately spacedtherefrom. The ends of member 8 and rod 5 comprise the electrodes orpoints of the spark plug across which the spark passes for ignition ofthe combustible mixture in the engine cylinder, not shown. Theelectrical potential is supplied to the points of the spark plug bysuitable generating means, not shown, through the metal structure of theengine block to electrode 8, referred to as the ground and by means ofthe lead wire 9 to electrode 5 as hereinafter described.

Insulator 4 serves to prevent dissipation of the electrical potentialbetween base I and rod 5 by shortcircuiting.

The condenser unit I 0 is connected in series with the spark plug and ispreferably of a capacity providing an improved spark characteristic.

' Condenser unit l0 comprises a series of metal discs ll having centralopenings therethrough and the metal end plates l2 and I3. The ceramiccylinder 14 encloses discs II and is closed and sealed at opposite endsby plates I 2 and I3. The ceramic members l5 are disposed intermediatediscs II and plates l2 and I3 to maintain the same in predeterminedspaced relation within cylinder l4.

Cylinder I4 is exhausted of air and is filled with an inert gas whichforms the dielectric of the condenser. In operation, the electricalpotential is passed through the condenser in the form' of a series ofspark-gaps bridging the spaces between the discs and plates.

The end of lead wire 9 is secured as by soldering to plate l2 ofcondenser ill for electrical connection therewith. Plate l3 of condenserl0 and the terminal clip l6 are connected by the wire ll which maysimilarly be soldered thereto.

The lead wire 9 is preferably formed by a large number of woven strandsof wire providing the necessary conductance and at the same timeaffording flexibility of the lead wire so as to allow for the usualinstallation and maintenance. Wire I1 is similarly constructed so as toallow limited relative movement of clip 16 and condenser unit l0according to the invention.

The single piece molded fitting I8 is formed of an elastic dielectricmaterial such as neoprene which is preferably impervious to water andoil. Fitting l8 includes the lower sleeve H! which is adapted to fitover insulator 4 and upper end of spark plug I. Clip I6 is disposed atthe inner end of the sleeve opening and includes a series of flexiblemembers 20 adapted to fit over terminal 6 and engage groove 1 of theterminal. The upper body 2| of fitting l8 encloses condenser unit Illand embraces the end portion of the insulating covering 22 of lead wire9.

Clip l6, wire I7 and condenser unit ID are embedded in body 2! offitting [8 at the time of molding of the latter to form a unitarystructure at the end of lead wire 9 which can be grasped firmly to befitted over the spark plug. Sleeve 19 provides the desired protection ofthe plug from moisture and oil which otherwise allows the electricalpotential to bridge insulator 4 and reduce the intensity of the sparkdischarge at the points. Clip [6 in addition toproviding the electricalconnection described, also serves to secure sleeve I9 over the sparkplug.

Condenser unit In is fully embedded in material forming the body Zl offitting l8 and is protected thereby against rough'handling and the likewhich might otherwise damage the -condenser. The condenser is fullyenclosed against the atmosphere and is particularly sealed ofi from thesleeve opening by the portion of fitting i8 between the condenser unitH3 and clip rs. Gases which tend to leak through insulator 4 around rod5 from the combustion chamber are allowed escape only into sleeve 19 andinto the atmosphere from the lower end of the sleeve.

The upper end of fitting I8 is molded 'over'the end of lead wire 9secured to plate [2 and embraces a substantial portion of'the covering22 which encloses lead wire 9. A bondis established between fitting l8and covering 22 which receives the stresses between these parts andrelieves .the condenser from any forces which might otherwise damage thesame.

The flexibility of lead wire 9 and wire 11 andv the elasticity of thematerial of fitting 18 allows condenser unit to float in the surroundingbody 2| of the fitting. Condenser unit [0 is thus insulated fromvibration, particularly of the engine in operation, and the terminalconnections made with plates I2 and I3 are relieved of .such stresses aswould either sever such connections or open the ends of the condenser.

The upper body 2| of fitting I8 may extend angularly of sleeve is andthe spark plug as desired or in a straight line with the sleeve [9 toaccommodate the particular engine design.

Various embodiments of the invention may be employed within the scope ofthe following claims.

I claim:

1. The combination in a device of the class described, which comprises aterminal fitting, a small-capacity sealed condenser unit, a flexibleelectrical conductor connecting said fitting and one terminal plate ofsaid condenser, a lead wire connected to the other terminal plate ofsaid condenser, an insulator covering said lead wire, and a solidelastic dielectric material embracing said terminal fitting and the endof said insulator covering and embedding said condenser and conductortherebetween and including a sleeve extending from the open end of saidterminal and adapted to receive and cover the upper end of an enginespark plug and to support said condenser, said elastic dielectricmaterial being of resilient material to protect said condenser againstdamage and breakdown by rough handling and en gine vibration.

2. A device of the class described comprising a small capacity condenserhaving a sealed gaseous dielectric and adapted to be connected in serieswith an engine spark plug, a spark plug shield of molded elasticdielectric material adapted to be fitted over the spark plug to protectthe same against moisture and carrying said condenser embedded thereinadjacent the upper end of the speak plug whereby said condenser isresiliently supported and protected against breakdown and damage as bythe vibration of the spark plug with engine operation.

3. In a'molded elastic shield fitting for a spark plug, a sleeve havingan opening for receiving the upper end of the spark plug, a terminalconnector at the inner end of said opening for connection with theterminal of the spark plug, a condenser embedded within said shieldfitting and spaced from said terminal connector, and flexible conductormeans electrically connecting said condenser and said fitting, saidshield supporting said condenser independently of said terminalconnector and spark plug with respect to normal engine vibration andbeing adapted to protect said condenser against damage and breakdown byrough handling and engine vibration.

ELMER C. KIEKHAEFER.

' References Cited in the file of this patent UNITED STATES PATENTSNumber Name Date 1,717,472 Stewart June 18, 1929 1,721,116 Henry July16, 1929 2,113,735 Mascuch Apr. 12, 1938 2,173,766 Ramsay Sept. 19, 19392,177,268 Stone Oct. 24, 1939

